/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Objects;
import com.google.common.base.Supplier;
import com.google.common.collect.Table.Cell;
import java.io.Serializable;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.Spliterator;
import java.util.function.BinaryOperator;
import java.util.stream.Collector;
import javax.annotation.Nullable;

/**
 * Provides static methods that involve a {@code Table}.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href= "https://github.com/google/guava/wiki/CollectionUtilitiesExplained#tables">
 * {@code Tables}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 7.0
 */
@GwtCompatible
public final class Tables {
    private Tables() {}

    /**
     * Returns a {@link Collector} that accumulates elements into a {@code Table} created using the
     * specified supplier, whose cells are generated by applying the provided mapping functions to
     * the input elements. Cells are inserted into the generated {@code Table} in encounter order.
     *
     * <p>
     * If multiple input elements map to the same row and column, an {@code IllegalStateException}
     * is thrown when the collection operation is performed.
     *
     * @since 21.0
     */
    @Beta
    public static <T, R, C, V, I extends Table<R, C, V>> Collector<T, ?, I> toTable(
            java.util.function.Function<? super T, ? extends R> rowFunction,
            java.util.function.Function<? super T, ? extends C> columnFunction,
            java.util.function.Function<? super T, ? extends V> valueFunction,
            java.util.function.Supplier<I> tableSupplier) {
        return toTable(rowFunction, columnFunction, valueFunction, (v1, v2) -> {
            throw new IllegalStateException("Conflicting values " + v1 + " and " + v2);
        }, tableSupplier);
    }

    /**
     * Returns a {@link Collector} that accumulates elements into a {@code Table} created using the
     * specified supplier, whose cells are generated by applying the provided mapping functions to
     * the input elements. Cells are inserted into the generated {@code Table} in encounter order.
     *
     * <p>
     * If multiple input elements map to the same row and column, the specified merging function is
     * used to combine the values. Like
     * {@link java.util.stream.Collectors#toMap(java.util.function.Function, java.util.function.Function, BinaryOperator, java.util.function.Supplier)},
     * this Collector throws a {@code
     * NullPointerException} on null values returned from {@code valueFunction}, and treats nulls
     * returned from {@code mergeFunction} as removals of that row/column pair.
     *
     * @since 21.0
     */
    public static <T, R, C, V, I extends Table<R, C, V>> Collector<T, ?, I> toTable(
            java.util.function.Function<? super T, ? extends R> rowFunction,
            java.util.function.Function<? super T, ? extends C> columnFunction,
            java.util.function.Function<? super T, ? extends V> valueFunction, BinaryOperator<V> mergeFunction,
            java.util.function.Supplier<I> tableSupplier) {
        checkNotNull(rowFunction);
        checkNotNull(columnFunction);
        checkNotNull(valueFunction);
        checkNotNull(mergeFunction);
        checkNotNull(tableSupplier);
        return Collector.of(tableSupplier, (table, input) -> merge(table, rowFunction.apply(input),
                columnFunction.apply(input), valueFunction.apply(input), mergeFunction), (table1, table2) -> {
                    for (Table.Cell<R, C, V> cell2 : table2.cellSet()) {
                        merge(table1, cell2.getRowKey(), cell2.getColumnKey(), cell2.getValue(), mergeFunction);
                    }
                    return table1;
                });
    }

    private static <R, C, V> void merge(Table<R, C, V> table, R row, C column, V value,
            BinaryOperator<V> mergeFunction) {
        checkNotNull(value);
        V oldValue = table.get(row, column);
        if (oldValue == null) {
            table.put(row, column, value);
        } else {
            V newValue = mergeFunction.apply(oldValue, value);
            if (newValue == null) {
                table.remove(row, column);
            } else {
                table.put(row, column, newValue);
            }
        }
    }

    /**
     * Returns an immutable cell with the specified row key, column key, and value.
     *
     * <p>
     * The returned cell is serializable.
     *
     * @param rowKey the row key to be associated with the returned cell
     * @param columnKey the column key to be associated with the returned cell
     * @param value the value to be associated with the returned cell
     */
    public static <R, C, V> Cell<R, C, V> immutableCell(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
        return new ImmutableCell<R, C, V>(rowKey, columnKey, value);
    }

    static final class ImmutableCell<R, C, V> extends AbstractCell<R, C, V> implements Serializable {
        private final R rowKey;
        private final C columnKey;
        private final V value;

        ImmutableCell(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
            this.rowKey = rowKey;
            this.columnKey = columnKey;
            this.value = value;
        }

        @Override
        public R getRowKey() {
            return rowKey;
        }

        @Override
        public C getColumnKey() {
            return columnKey;
        }

        @Override
        public V getValue() {
            return value;
        }

        private static final long serialVersionUID = 0;
    }

    abstract static class AbstractCell<R, C, V> implements Cell<R, C, V> {
        // needed for serialization
        AbstractCell() {}

        @Override
        public boolean equals(Object obj) {
            if (obj == this) {
                return true;
            }
            if (obj instanceof Cell) {
                Cell<?, ?, ?> other = (Cell<?, ?, ?>) obj;
                return Objects.equal(getRowKey(), other.getRowKey())
                        && Objects.equal(getColumnKey(), other.getColumnKey())
                        && Objects.equal(getValue(), other.getValue());
            }
            return false;
        }

        @Override
        public int hashCode() {
            return Objects.hashCode(getRowKey(), getColumnKey(), getValue());
        }

        @Override
        public String toString() {
            return "(" + getRowKey() + "," + getColumnKey() + ")=" + getValue();
        }
    }

    /**
     * Creates a transposed view of a given table that flips its row and column keys. In other
     * words, calling {@code get(columnKey, rowKey)} on the generated table always returns the same
     * value as calling {@code
     * get(rowKey, columnKey)} on the original table. Updating the original table changes the
     * contents of the transposed table and vice versa.
     *
     * <p>
     * The returned table supports update operations as long as the input table supports the
     * analogous operation with swapped rows and columns. For example, in a {@link HashBasedTable}
     * instance, {@code
     * rowKeySet().iterator()} supports {@code remove()} but {@code
     * columnKeySet().iterator()} doesn't. With a transposed {@link HashBasedTable}, it's the other
     * way around.
     */
    public static <R, C, V> Table<C, R, V> transpose(Table<R, C, V> table) {
        return (table instanceof TransposeTable) ? ((TransposeTable<R, C, V>) table).original
                : new TransposeTable<C, R, V>(table);
    }

    private static class TransposeTable<C, R, V> extends AbstractTable<C, R, V> {
        final Table<R, C, V> original;

        TransposeTable(Table<R, C, V> original) {
            this.original = checkNotNull(original);
        }

        @Override
        public void clear() {
            original.clear();
        }

        @Override
        public Map<C, V> column(R columnKey) {
            return original.row(columnKey);
        }

        @Override
        public Set<R> columnKeySet() {
            return original.rowKeySet();
        }

        @Override
        public Map<R, Map<C, V>> columnMap() {
            return original.rowMap();
        }

        @Override
        public boolean contains(@Nullable Object rowKey, @Nullable Object columnKey) {
            return original.contains(columnKey, rowKey);
        }

        @Override
        public boolean containsColumn(@Nullable Object columnKey) {
            return original.containsRow(columnKey);
        }

        @Override
        public boolean containsRow(@Nullable Object rowKey) {
            return original.containsColumn(rowKey);
        }

        @Override
        public boolean containsValue(@Nullable Object value) {
            return original.containsValue(value);
        }

        @Override
        public V get(@Nullable Object rowKey, @Nullable Object columnKey) {
            return original.get(columnKey, rowKey);
        }

        @Override
        public V put(C rowKey, R columnKey, V value) {
            return original.put(columnKey, rowKey, value);
        }

        @Override
        public void putAll(Table<? extends C, ? extends R, ? extends V> table) {
            original.putAll(transpose(table));
        }

        @Override
        public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
            return original.remove(columnKey, rowKey);
        }

        @Override
        public Map<R, V> row(C rowKey) {
            return original.column(rowKey);
        }

        @Override
        public Set<C> rowKeySet() {
            return original.columnKeySet();
        }

        @Override
        public Map<C, Map<R, V>> rowMap() {
            return original.columnMap();
        }

        @Override
        public int size() {
            return original.size();
        }

        @Override
        public Collection<V> values() {
            return original.values();
        }

        // Will cast TRANSPOSE_CELL to a type that always succeeds
        private static final Function<Cell<?, ?, ?>, Cell<?, ?, ?>> TRANSPOSE_CELL =
                new Function<Cell<?, ?, ?>, Cell<?, ?, ?>>() {
                    @Override
                    public Cell<?, ?, ?> apply(Cell<?, ?, ?> cell) {
                        return immutableCell(cell.getColumnKey(), cell.getRowKey(), cell.getValue());
                    }
                };

        @SuppressWarnings("unchecked")
        @Override
        Iterator<Cell<C, R, V>> cellIterator() {
            return Iterators.transform(original.cellSet().iterator(), (Function) TRANSPOSE_CELL);
        }

        @SuppressWarnings("unchecked")
        @Override
        Spliterator<Cell<C, R, V>> cellSpliterator() {
            return CollectSpliterators.map(original.cellSet().spliterator(), (Function) TRANSPOSE_CELL);
        }
    }

    /**
     * Creates a table that uses the specified backing map and factory. It can generate a table
     * based on arbitrary {@link Map} classes.
     *
     * <p>
     * The {@code factory}-generated and {@code backingMap} classes determine the table iteration
     * order. However, the table's {@code row()} method returns instances of a different class than
     * {@code factory.get()} does.
     *
     * <p>
     * Call this method only when the simpler factory methods in classes like {@link HashBasedTable}
     * and {@link TreeBasedTable} won't suffice.
     *
     * <p>
     * The views returned by the {@code Table} methods {@link Table#column},
     * {@link Table#columnKeySet}, and {@link Table#columnMap} have iterators that don't support
     * {@code remove()}. Otherwise, all optional operations are supported. Null row keys, columns
     * keys, and values are not supported.
     *
     * <p>
     * Lookups by row key are often faster than lookups by column key, because the data is stored in
     * a {@code Map<R, Map<C, V>>}. A method call like {@code column(columnKey).get(rowKey)} still
     * runs quickly, since the row key is provided. However, {@code column(columnKey).size()} takes
     * longer, since an iteration across all row keys occurs.
     *
     * <p>
     * Note that this implementation is not synchronized. If multiple threads access this table
     * concurrently and one of the threads modifies the table, it must be synchronized externally.
     *
     * <p>
     * The table is serializable if {@code backingMap}, {@code factory}, the maps generated by
     * {@code factory}, and the table contents are all serializable.
     *
     * <p>
     * Note: the table assumes complete ownership over of {@code backingMap} and the maps returned
     * by {@code factory}. Those objects should not be manually updated and they should not use
     * soft, weak, or phantom references.
     *
     * @param backingMap place to store the mapping from each row key to its corresponding column
     *        key / value map
     * @param factory supplier of new, empty maps that will each hold all column key / value
     *        mappings for a given row key
     * @throws IllegalArgumentException if {@code backingMap} is not empty
     * @since 10.0
     */
    @Beta
    public static <R, C, V> Table<R, C, V> newCustomTable(Map<R, Map<C, V>> backingMap,
            Supplier<? extends Map<C, V>> factory) {
        checkArgument(backingMap.isEmpty());
        checkNotNull(factory);
        // TODO(jlevy): Wrap factory to validate that the supplied maps are empty?
        return new StandardTable<R, C, V>(backingMap, factory);
    }

    /**
     * Returns a view of a table where each value is transformed by a function. All other properties
     * of the table, such as iteration order, are left intact.
     *
     * <p>
     * Changes in the underlying table are reflected in this view. Conversely, this view supports
     * removal operations, and these are reflected in the underlying table.
     *
     * <p>
     * It's acceptable for the underlying table to contain null keys, and even null values provided
     * that the function is capable of accepting null input. The transformed table might contain
     * null values, if the function sometimes gives a null result.
     *
     * <p>
     * The returned table is not thread-safe or serializable, even if the underlying table is.
     *
     * <p>
     * The function is applied lazily, invoked when needed. This is necessary for the returned table
     * to be a view, but it means that the function will be applied many times for bulk operations
     * like {@link Table#containsValue} and {@code Table.toString()}. For this to perform well,
     * {@code function} should be fast. To avoid lazy evaluation when the returned table doesn't
     * need to be a view, copy the returned table into a new table of your choosing.
     *
     * @since 10.0
     */
    @Beta
    public static <R, C, V1, V2> Table<R, C, V2> transformValues(Table<R, C, V1> fromTable,
            Function<? super V1, V2> function) {
        return new TransformedTable<R, C, V1, V2>(fromTable, function);
    }

    private static class TransformedTable<R, C, V1, V2> extends AbstractTable<R, C, V2> {
        final Table<R, C, V1> fromTable;
        final Function<? super V1, V2> function;

        TransformedTable(Table<R, C, V1> fromTable, Function<? super V1, V2> function) {
            this.fromTable = checkNotNull(fromTable);
            this.function = checkNotNull(function);
        }

        @Override
        public boolean contains(Object rowKey, Object columnKey) {
            return fromTable.contains(rowKey, columnKey);
        }

        @Override
        public V2 get(Object rowKey, Object columnKey) {
            // The function is passed a null input only when the table contains a null
            // value.
            return contains(rowKey, columnKey) ? function.apply(fromTable.get(rowKey, columnKey)) : null;
        }

        @Override
        public int size() {
            return fromTable.size();
        }

        @Override
        public void clear() {
            fromTable.clear();
        }

        @Override
        public V2 put(R rowKey, C columnKey, V2 value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putAll(Table<? extends R, ? extends C, ? extends V2> table) {
            throw new UnsupportedOperationException();
        }

        @Override
        public V2 remove(Object rowKey, Object columnKey) {
            return contains(rowKey, columnKey) ? function.apply(fromTable.remove(rowKey, columnKey)) : null;
        }

        @Override
        public Map<C, V2> row(R rowKey) {
            return Maps.transformValues(fromTable.row(rowKey), function);
        }

        @Override
        public Map<R, V2> column(C columnKey) {
            return Maps.transformValues(fromTable.column(columnKey), function);
        }

        Function<Cell<R, C, V1>, Cell<R, C, V2>> cellFunction() {
            return new Function<Cell<R, C, V1>, Cell<R, C, V2>>() {
                @Override
                public Cell<R, C, V2> apply(Cell<R, C, V1> cell) {
                    return immutableCell(cell.getRowKey(), cell.getColumnKey(), function.apply(cell.getValue()));
                }
            };
        }

        @Override
        Iterator<Cell<R, C, V2>> cellIterator() {
            return Iterators.transform(fromTable.cellSet().iterator(), cellFunction());
        }

        @Override
        Spliterator<Cell<R, C, V2>> cellSpliterator() {
            return CollectSpliterators.map(fromTable.cellSet().spliterator(), cellFunction());
        }

        @Override
        public Set<R> rowKeySet() {
            return fromTable.rowKeySet();
        }

        @Override
        public Set<C> columnKeySet() {
            return fromTable.columnKeySet();
        }

        @Override
        Collection<V2> createValues() {
            return Collections2.transform(fromTable.values(), function);
        }

        @Override
        public Map<R, Map<C, V2>> rowMap() {
            Function<Map<C, V1>, Map<C, V2>> rowFunction = new Function<Map<C, V1>, Map<C, V2>>() {
                @Override
                public Map<C, V2> apply(Map<C, V1> row) {
                    return Maps.transformValues(row, function);
                }
            };
            return Maps.transformValues(fromTable.rowMap(), rowFunction);
        }

        @Override
        public Map<C, Map<R, V2>> columnMap() {
            Function<Map<R, V1>, Map<R, V2>> columnFunction = new Function<Map<R, V1>, Map<R, V2>>() {
                @Override
                public Map<R, V2> apply(Map<R, V1> column) {
                    return Maps.transformValues(column, function);
                }
            };
            return Maps.transformValues(fromTable.columnMap(), columnFunction);
        }
    }

    /**
     * Returns an unmodifiable view of the specified table. This method allows modules to provide
     * users with "read-only" access to internal tables. Query operations on the returned table
     * "read through" to the specified table, and attempts to modify the returned table, whether
     * direct or via its collection views, result in an {@code UnsupportedOperationException}.
     *
     * <p>
     * The returned table will be serializable if the specified table is serializable.
     *
     * <p>
     * Consider using an {@link ImmutableTable}, which is guaranteed never to change.
     *
     * @since 11.0
     */
    public static <R, C, V> Table<R, C, V> unmodifiableTable(Table<? extends R, ? extends C, ? extends V> table) {
        return new UnmodifiableTable<R, C, V>(table);
    }

    private static class UnmodifiableTable<R, C, V> extends ForwardingTable<R, C, V> implements Serializable {
        final Table<? extends R, ? extends C, ? extends V> delegate;

        UnmodifiableTable(Table<? extends R, ? extends C, ? extends V> delegate) {
            this.delegate = checkNotNull(delegate);
        }

        @SuppressWarnings("unchecked") // safe, covariant cast
        @Override
        protected Table<R, C, V> delegate() {
            return (Table<R, C, V>) delegate;
        }

        @Override
        public Set<Cell<R, C, V>> cellSet() {
            return Collections.unmodifiableSet(super.cellSet());
        }

        @Override
        public void clear() {
            throw new UnsupportedOperationException();
        }

        @Override
        public Map<R, V> column(@Nullable C columnKey) {
            return Collections.unmodifiableMap(super.column(columnKey));
        }

        @Override
        public Set<C> columnKeySet() {
            return Collections.unmodifiableSet(super.columnKeySet());
        }

        @Override
        public Map<C, Map<R, V>> columnMap() {
            Function<Map<R, V>, Map<R, V>> wrapper = unmodifiableWrapper();
            return Collections.unmodifiableMap(Maps.transformValues(super.columnMap(), wrapper));
        }

        @Override
        public V put(@Nullable R rowKey, @Nullable C columnKey, @Nullable V value) {
            throw new UnsupportedOperationException();
        }

        @Override
        public void putAll(Table<? extends R, ? extends C, ? extends V> table) {
            throw new UnsupportedOperationException();
        }

        @Override
        public V remove(@Nullable Object rowKey, @Nullable Object columnKey) {
            throw new UnsupportedOperationException();
        }

        @Override
        public Map<C, V> row(@Nullable R rowKey) {
            return Collections.unmodifiableMap(super.row(rowKey));
        }

        @Override
        public Set<R> rowKeySet() {
            return Collections.unmodifiableSet(super.rowKeySet());
        }

        @Override
        public Map<R, Map<C, V>> rowMap() {
            Function<Map<C, V>, Map<C, V>> wrapper = unmodifiableWrapper();
            return Collections.unmodifiableMap(Maps.transformValues(super.rowMap(), wrapper));
        }

        @Override
        public Collection<V> values() {
            return Collections.unmodifiableCollection(super.values());
        }

        private static final long serialVersionUID = 0;
    }

    /**
     * Returns an unmodifiable view of the specified row-sorted table. This method allows modules to
     * provide users with "read-only" access to internal tables. Query operations on the returned
     * table "read through" to the specified table, and attempts to modify the returned table,
     * whether direct or via its collection views, result in an
     * {@code UnsupportedOperationException}.
     *
     * <p>
     * The returned table will be serializable if the specified table is serializable.
     *
     * @param table the row-sorted table for which an unmodifiable view is to be returned
     * @return an unmodifiable view of the specified table
     * @since 11.0
     */
    @Beta
    public static <R, C, V> RowSortedTable<R, C, V> unmodifiableRowSortedTable(
            RowSortedTable<R, ? extends C, ? extends V> table) {
        /*
         * It's not ? extends R, because it's technically not covariant in R. Specifically,
         * table.rowMap().comparator() could return a comparator that only works for the ? extends
         * R. Collections.unmodifiableSortedMap makes the same distinction.
         */
        return new UnmodifiableRowSortedMap<R, C, V>(table);
    }

    static final class UnmodifiableRowSortedMap<R, C, V> extends UnmodifiableTable<R, C, V>
            implements RowSortedTable<R, C, V> {

        public UnmodifiableRowSortedMap(RowSortedTable<R, ? extends C, ? extends V> delegate) {
            super(delegate);
        }

        @Override
        protected RowSortedTable<R, C, V> delegate() {
            return (RowSortedTable<R, C, V>) super.delegate();
        }

        @Override
        public SortedMap<R, Map<C, V>> rowMap() {
            Function<Map<C, V>, Map<C, V>> wrapper = unmodifiableWrapper();
            return Collections.unmodifiableSortedMap(Maps.transformValues(delegate().rowMap(), wrapper));
        }

        @Override
        public SortedSet<R> rowKeySet() {
            return Collections.unmodifiableSortedSet(delegate().rowKeySet());
        }

        private static final long serialVersionUID = 0;
    }

    @SuppressWarnings("unchecked")
    private static <K, V> Function<Map<K, V>, Map<K, V>> unmodifiableWrapper() {
        return (Function) UNMODIFIABLE_WRAPPER;
    }

    private static final Function<? extends Map<?, ?>, ? extends Map<?, ?>> UNMODIFIABLE_WRAPPER =
            new Function<Map<Object, Object>, Map<Object, Object>>() {
                @Override
                public Map<Object, Object> apply(Map<Object, Object> input) {
                    return Collections.unmodifiableMap(input);
                }
            };

    /**
     * Returns a synchronized (thread-safe) table backed by the specified table. In order to
     * guarantee serial access, it is critical that <b>all</b> access to the backing table is
     * accomplished through the returned table.
     *
     * <p>
     * It is imperative that the user manually synchronize on the returned table when accessing any
     * of its collection views:
     *
     * <pre>
     * {@code
     * Table<R, C, V> table = Tables.synchronizedTable(HashBasedTable.<R, C, V>create());
     * ...
     * Map<C, V> row = table.row(rowKey);  // Needn't be in synchronized block
     * ...
     * synchronized (table) {  // Synchronizing on table, not row!
     *   Iterator<Map.Entry<C, V>> i = row.entrySet().iterator(); // Must be in synchronized block
     *   while (i.hasNext()) {
     *     foo(i.next());
     *   }
     * }
     * }
     * </pre>
     *
     * <p>
     * Failure to follow this advice may result in non-deterministic behavior.
     *
     * <p>
     * The returned table will be serializable if the specified table is serializable.
     *
     * @param table the table to be wrapped in a synchronized view
     * @return a synchronized view of the specified table
     * @since 22.0
     */
    public static <R, C, V> Table<R, C, V> synchronizedTable(Table<R, C, V> table) {
        return Synchronized.table(table, null);
    }

    static boolean equalsImpl(Table<?, ?, ?> table, @Nullable Object obj) {
        if (obj == table) {
            return true;
        } else if (obj instanceof Table) {
            Table<?, ?, ?> that = (Table<?, ?, ?>) obj;
            return table.cellSet().equals(that.cellSet());
        } else {
            return false;
        }
    }
}
